Popups/popunders issues, rewinding on random keystrokes

First things first, I really like Vivaldi. And so on. Praise praise. I have some issues though. Vivaldi 1.2.490.43, 32bit Windows 10 Pro 64bit 1. Popunders/popups/ads opened in new tabs ... stay with me. For one Vivaldi is not as good as blocking them as other browsers (Firefox, IE, Edge). And once I hit one of them, it will randomly come up until I reinstall the browser and encounter it again. I don't have malware or anything (fresh legit Windows install), it's just like those functions stay behind somehow, even after clearing history/cache. Reinstalling the entire thing seems to be the only way to get rid of them. 2. Keystrokes randomly triggers the "rewind" function. It only happens, so far, on one site I visit though, techpowerup.com (powered by xenforo). It can be any keystroke, but it seems to happen more often when I hit backspace. At first I thought it was a browser function or something, or that I hit enter and it somehow acted on where the cursor was, but that is not the case. It actually is random. A nitpick is that the Lastpass addon is truly slow to login, but that might not be related. Oh, btw, it would be nice if there was an option for the right click -> Open in new tab function to behave like ctrl-click. Unless I missed it. Anyway that is probably a different topic.